|Dear Dr Vesala et al.,|
This manuscript presents the first very long term record of carbonyl sulfide (OCS) eddy flux covariance over any ecosystem. Additionally, measurements of OCS exchange in the boreal region are nearly as rare. Even without any analysis, the dataset is valuable to our scientific community. That said, the analysis performed here is the first step of many. A typical motivation for measuring OCS over ecosystems is to reveal new information about the carbon cycle which can be in turn used to constrain the representation of land carbon uptake in land surface models, mentioned in the introduction. The analysis here incorporates the role that stomatal conductance and leaf-affecting parameters play in OCS uptake by vegetation; however, the data is not brought back around to compare to CO2 fluxes. I hope to see this in a future effort!
In the response to my earlier review, you note that deriving stomatal conductance from OCS measurements is “a very difficult task to do from EC” and requires its own paper. Rick Wehr may have already written this paper in 2017. As far as I can tell, the most difficult part of applying Wehr et al., (2017) approach here is coming up with a reasonable estimate of mesophyll conductance for Scots Pine, which has experienced recent advances (see Stangl et al. 2021). Wehr and Saleska (2021) have also developed an improved method for estimating stomatal conductance from CO2 EC measurements that can be compared to OCS-based estimates.
Thank you for your continued effort in improving this manuscript.
Stangl, Z.R., Tarvainen, L., Wallin, G. and Marshall, J.D. (2022), Limits to photosynthesis: seasonal shifts in supply and demand for CO2 in Scots pine. New Phytol, 233: 1108-1120. https://doi.org/10.1111/nph.17856
Wehr, R., Saleska, S. (2021) Calculating canopy stomatal conductance from eddy covariance measurements, in light of th energy budget closure problem. Biogeosciences, 18: 13–24.